This question has been put on hold at 18:36 server time. I have posted an answer to it at 18:59 server time. Which should not be possible.
I have started writing an answer when the question was still open. My guess is, the system checked whether or not an answer may be posted when it let me to start answering, rather than when I've finished writing and clicked "post".
It's not the system's intended behaviour, is it?